Electrolytic rectifier



Sept. 4, 1928. 1,682,846

H. c. KREMERS ELECTROLYTIC RECTIFIER Filed July 16, 1926 INVENTOR f/arg/C Kre/77ers ATTOR H EYS Patented Sept. 4, 1928.

UNITED STATES PATENT FFEQ.

HARRY C. KREMERS, OF UBBLNA, LLINCIS.

ELECTROLYTIC RECTIFIER.

Application filed July 1S,

y :consist of al group of elements, located in the third periodic groupand resembling each other rather closely chemically andphysical- Y ly.'The' rareearth group consists of the followingelementsarranged inAthree groupings the ceriunrgroup, includingl lanthanum, ceri- "um,1praseodymium, neodymium,'illinium and sa rium the terbium group,.including'europium, 1gadoliniun'i, terbium; and the yttrium group,including dys'prosium, holmium, yttrium, erbium, thulium, ytterbium,lutecium and scandium. v

In the occurrence of these elements in nature, the cerium group withsmall amounts of the terbium group and in most cases with lesser amountsof the yttrium group is found in such minerals asA monazite sand.ceritc, ctc. Likewise the yttriu'm group with vsmall amounts of theterbium group and still'lesscr amounts ofthe cerium group is found inminerals such as gadolinite, fergusonite, etc.

Thust-here can be obtained Without much eiforttwo rather distinct groupsof rare earth metals: thecerium group proper with some ltei'bium groupmaterial, and the yttrium group proper, also with some terbium groupmaterial. With the exception of cerium, the separation and preparationof the individual elements of any one of the three groups mentioned is avery slou7 and difiicult task. Since theelements of the cerium group areso similar in nature, the entire group may be reduced to metal. Thismetal appears on the marketl in an alloy known as misch metal(mixedmetal). The chemical properties ot misch metal are quite similarto that of any vone of the individual elements. This com mercial mischmetal as it appears on the market Yhas usually the following approximatecomposition: lanthanum-20%, cerium-35%, neodylnium-QOf/Vf, praseodymi-11m- 57%, @madam-10%, terbium group- 7% and. yttrium group-3%. Theyttrium group has also been reduced to metal in an experimental Way onlyand called yttrium mixed metal.

In experimenting with various alloys ot the rare earth metals, andparticularly misch metal, it has been discovered that if two brightlypolished plates of such metal are vdue to, the formation of a 1926.Serial No. 122,802.

placed in an elcctrolytic solution and the two plates connected to theterminals of an electric battery or other source of unidirectionalvoltage, an instantaneous How of current occurs. After a few minutes thecurrent is found to drop ofi' to a negligible value, such l. the drop.inthe curas a few milli-amperes. rent being accompanied by, andapparently film of oxide on rare earth metal the posit-ive batanode isallowed before it is subthe metal anode, that is, the plate which isconnected to tery terminal. If the metal to tarnish or oxidize in airmerged in the electrolyte, the current flow is very small or negligiblewhen the battery is first connected thereto.

It has been further observed that the rare earth metal plate which isused as a cathode, that is, the plate connected to the negative batteryterminal, acts as a good cond ctor of electric current from theelectrolyte. Thus, it is seen that the rare earth metals behave asconductors when they function as cathodcs and behave as non-conductorswhen they function as anodes` The anode used to produce this effect maybe composed of any one of the rare earth metals alone, such as cerium,lanthanum, praseodymium or neodymium, or may comprise an alloy of one ofthese metals or an alloy of misch metal. The electrolyte used may be asolution of sodium or potassium hydroxide, sodium phosphate. borax,boric acid or certain neutral or alkaline salt sollitions or mixturescomposed or" alkalies and salts.

It a cell using a non-corrosive or non-filming electrode or plate suchas lead or carbon, a misch metal plate and an electrolyte, (as mentionedabove) preferably sodi um4 hydroxide solution, is connected by means ofthe lead and misch metal plates to an alternating current ot a suitablevoltage, the current flow in one direction is almost entirely shut oiland a direct pulsating current is obtained. In such an arrangement theflow of current is accompanied by an elcctrolytic action in the cell,with evolution of hydrogen gas at the misch metal and oxygen gas at thelead. The action ofthe misch metal (or other rare earth metals) is suchthat electrons are permitted to flow from the misch metal plate torelease hydrogen ions but are prevented from passing from oxygen ionsinto the solution.

It is an object of the present invention to provide an electrolyticrectifier employing as an electrode one of the ra re earth metals or analloy or mixture of several or all of such metals, together with asuitable electrolyte.

It is a further object of this invention to provide an electrolyticrectifier of this type which may be used to convert an alternatingcurrent into a unidirectional current which is suitable for chargingstorage batteries, operating radio apparatus and for other puroses. v Y

It is further contemplated to provide the electrolytic cell employingelectrodes of rare earth metal or metals which may be f,used as alightning arrester, as an electrolytic condenser Aorfor any otherApurposev or function to whichelectrolytie cells are applicable.

, In describing the invention in detail, reference will be made to theaccompanying drawings, in which Figure 1 represents, in a diagrammaticand simplified manner, an electrolytic rectifier embodyingthe presentinvention;

Figure 2'1rlepresents a modified form of electrolyticrectifier'desig'ned to rectify the full alternating current wave; andAFigure 3 shows a further modification of the invention employing amultiplicity of electrolytie cells connected in series and provided withmeans for eliminating undesirable fluctuations in the output current.

The electrolytic. cell of the present inven tion will now be describedas used in.conneetion with the rectification of alternating currents, itbeing understood that this represents only one manner in which this cellmay be employed, and that the cell may be used in various other ways. InFig. l o f the drawings, a source of alternating current is connected asshown to the primary winding of the transformer 1, the secondary circuitof which includes in series therewith an electrolytic cell Z comprisinga suitable electrolyte as described above, a rare earth metal plate 3and a plate 4 of carbon lead or other suitable non-corrosive material.The sccondary circuit including the cell in .series may be connected tothe negative terminal 5 and the positive terminal 6 of the storagebattery whereby such battery may be charged, or this secondary circuitmay be connected to any other device, circuit or apparatus requiring aunidirectional current for its operation. The cell 2 being in series inthe secondary circuit allows current to flow in one direction only, thusrectfying one half of the alternating current waves.

By the use of two plates of rare earth metal1 shown at 7 and 7 in Fig.2, with a single plate 8 of carbon, lead or other suitable material, thefull alternating current wave may be rectified. In this arrangement, theplates 7 and 7 are connected to the opposite terminals of the secondarywinding of the transformer 10, the direct current output circuit beingconnected between the carbon plate 8 and a center tap 9 of thetransformer secondary. In this arrangement current may How from the tap9 through the external direct current circuit, returning to one or theother of the plates 7 and 7 through the carbon plate 8 and theelectrolyte, the return of the current in the reverse direct-ion beingprevented by the action of the rare earth metal electrodes as describedabove.

In the modification shown in Fig. 3, the secondary winding of atransformer 11 has its terminals connected to two batteries, 12 and 12of electrolytic cells of the'type describedh the individual cells ofeach battery being connectcd in series. The return of the direct currentoutput circuit is connected to a'center tap of the transformersecondary, and the operation of this arrangement issimilar to that ofthe arrangement shown? in Fig'. 2. The output circuit of this rectifiermay be provided with asuitable filter circuit,such `as the condenscrs 13and 13 and the series connected choke coil 14, this filter circuitacting in the well known manner to suppress or choke outVA variations orripples in the rectified current. The form and -arrangeriient of therectifier shown in Fig.l 3 is particularly applicable to radio work inwhich a comparatively high voltage is required in connection with thewell known A andB circuits of audion tubes. The use of several cells inseries permits the rectifica-tion of a zcomparatively high voltage, asthe voltage of the secondary circuit is tributed over several cells inseries.

It has been found that various alkaline solutions may be used as theelectrolyte in the electrolytic cells of the -present invention. Onesolution -which gives very satisfactory results is a 25% solution ofsodium hydroxide and water, although various other sodium hydroxidesolutions give satisfactory results.

The rectifier con=tructed in accordance with the present invention hasmany advantages over the now known types of electrolytic rectificrs. Theefficiency of the present. rectifier is found to be very much betterthan the efficiency of the usual aluminum element rectifier, beingsubstantially equal to the efficicncy of a rectifier of the electronvalve, or tantalum electrode type. In addition, the rectifier of thepresent invention canbe manufactured at a much lower cost than can thcrectifiers of the electron valve or tantalum type, the misch metal beingreadily obtainable at a comparatively low price.

The rectifiers constructed in accordance with the present invention areparticularly applicable t0 use in connection with charging storagebatteries, in electrodeposition of metal, and in other electro-chemicalreactions, and also in radio work, but these recti fiers are also welladapted for use wherever direct current is required and an alternatingcurrent. supply is available. The electrolytic cells may also be used inelectrolytic lightning dis- .Y

1,682,846 3 arresters of the Well known type, two rare non-filmingconducting material, a filming earth metal plates or electrodes beingsubmerged in a suitable electrolyte and acting to resist the flow ofcurrent until a predetermined high voltage is impressed between theplates.

Although the present invention has been described in connection withcertain .specific apparatus and devices, it should be understood thatthe cell of the present invention, and the action between the rare earthmetals and the electrolyte therein is capable of general application,and the invention is therefore not limited to the specific embodiment-sshown. The cells may be provided with any suitable number andarrangement of both rare earth metal and non-filming electrodes, themeta-l used for the filming electrode may be varied as described above,and the electrolyte used may be any suitable alkaline salt solution.Moreover, the connection between the electrodes and the cells may bevaried to suit the desired opera-tion of the device, and many otherchanges, Amodifications and combinations may be made without departingfrom the scope of the invention as defined by the appended claims. f

I claim:

l. In an electrol tic cell, a lming electrode of rare earth metal.

2. In an electrolytic cell containing an electrolyte, a filmingelectrode composed at least in part of rare earth metal.

3. In an electrolytic cell containing an electrolyte of alkaline saltsolution, a filming electrode of rare earth metal including cerium.

4. In an electrolytic cell containing an electrolyte and having at leastone electrode of electrode of rare earth metal.

5. In an electrolytie cell containing an electrolyte and having at leastone electrode of non-filming conducting material, al filming electrodecontaining cerium.

6. In an electrolytic cell containing an electrode of non-corrosivemetal and an electrolyte of alkaline salt solution including sodiumhydroxide, a filming electrode composed at least in part of cerium.

7. In an electrolytic cell having an electrode of non-corrosive metaland an electrolyte including sodium hydroxide, a filming electrodecomprising a mixture of rare earth metals from the cerium, terbium andyttrium groups.

8. In a rectifier comprising a source of alternating current and anelectrolytic cell connected in series therewith, a filming electrodecomposed at least in part of rare earth metal.

9. In an electrolyt-ic cell having an electrode of lead submerged in anelectrolytic solution including sodium hydroxide, a. filming electrodecomposed of rare earth metals including cerium, lantlianum andneodymium.

l0. A filming electrode composed of rare earth metal.

1l. A filming electrode composed at leastin part of cerium.

l2. A filming electrode composed of rare earth metals from the cerium,terbium and yttrium groups.

13. A filming electrode composed of rare earth metals includingr cerium,lanthanum and neodymium.

In testimony whereof I aflix my signature.

HARRY C. KREMERS.

